A hacker secretly took over a computer server at the BBC, Britain's public broadcaster, and then launched a Christmas Day campaign to convince other cybercriminals to pay him for access to the system.
While it was not known if the hacker found any buyers, the BBC's security team responded to the issue on Saturday and believed it had secured the site, according to a person familiar with the clean-up effort.
A BBC spokesman declined to discuss the incident. It could not be determined whether the hackers stole data or caused any damage in the attack, which compromised a server that manages a password-protected website.
It was not clear how the BBC, the world's oldest and largest broadcaster, uses that site, ftp.bbc.co.uk  though ftp systems are typically used to manage the transfer of large data files over the internet.
The attack was first identified by Hold Security, a cybersecurity firm in the American city of Milwaukee that monitors underground cybercrime forums in search of stolen information.
The firm's researchers observed a notorious Russian hacker, known by the monikers "HASH" and "Rev0lver", attempting to sell access to the BBC server on December 25, according to Hold Security's founder and chief information security officer, Alex Holden. HASH sought to convince hackers that he had infiltrated the site by showing them files that could only be accessed by somebody who really controlled it, Holden said.
So far, Hold Security researchers had found no evidence the conversations led to a deal or that data was stolen from the BBC, Holden said. It is common for hackers to buy and sell access to compromised servers on underground forums.
Buyers view the access as a commodity that grants them the chance to further penetrate the victim organisation. They can also use compromised servers to set up command-and-control centres for cybercrime operations known as botnets, run spam campaigns or launch attacks to knock websites offline.
The BBC offer stood out because the media company was such a high-profile organisation, Holden said. "It's definitely a notch in someone's belt."